1. Field of the Invention
The invention relates to optical camera systems for nondestructive internal inspection of industrial gas turbines and other power generation machinery, including by way of non-limiting example steam turbines and generators. More particularly, aspects of the invention relate to an optical camera inspection system that is capable of positioning the camera field of view (FOV) through a gas turbine combustor and transition and capturing images of Row 1 rotating turbine blades while the turbine engine is in turning gear mode, with or without human intervention. In some embodiments, camera positioning and image capture can be initiated automatically or after receipt of operator permission. In other embodiments camera positioning can be performed manually.
2. Description of the Prior Art
Power generation machinery, such as steam or gas turbines, are often operated continuously with scheduled inspection and maintenance periods, at which time the turbine is taken off line and shut down. By way of example, a gas turbine engine often will be operated to generate power continuously for approximately 4000 hours, thereupon it is taken off line for routine maintenance, inspection, and repair of any components identified during inspection. Taking a gas turbine off line and eventually shutting it down completely for scheduled maintenance is a multi-day project. Some turbine components, such as the turbine rotor section, are operated at temperatures exceeding 1000° C. (1832° F.). The turbine requires 48-72 hours of cooling time to achieve ambient temperature before complete shutdown in order to reduce likelihood of component warping or other deformation. During the shutdown phase the turbine rotor rotational speed is spooled down from operating speed of approximately 3600 RPM to a speed of approximately 120 RPM or less in “turning gear mode”, where the rotor is externally driven by an auxiliary drive motor, in order to reduce likelihood of rotor warping. Other turbine components, such as the turbine housing, are also cooled slowly to ambient temperature.
Once the turbine is cooled to ambient temperature over the course of up to approximately 72 hours internal components of the now static turbine can be inspected with known optical camera inspection systems. Known optical camera inspection systems employ rigid or flexible optical bore scopes that are inserted into inspection ports located about the turbine periphery. The bore scope is manually positioned so that its field of view encompasses an area of interest within the turbine, such as one or more vanes or blades, combustor baskets, etc. A camera optically coupled to the bore scope captures images of objects of interest within the field of view for remote visualization and archiving (if desired) by an inspector.
If a series of different images of different areas of interest within a given turbine inspection port are desired, the operator must manually re-position the camera inspection system bore scope to achieve the desired relative alignment of internal area of interest and the field of view. Relative alignment can be achieved by physically moving the bore scope so that its viewing port is positioned proximal a static area of interest. Examples of such relative movement of bore scope and static turbine component are by inserting a bore scope in different orientations within a static combustor or radially in and out of space between a vane and blade row within the turbine section. Relative alignment can also be achieved by maintaining the bore scope viewing port in a static position and moving the turbine internal component of interest into the static viewing field. An example of relative movement of turbine internal component and static bore scope is inspection of different blades within a blade row by manually rotating the turbine rotor sequentially a few degrees and capturing the image of a blade. The rotor is rotated sequentially to align each desired individual blade in the row within the camera viewing field.
Complete turbine inspection requires multiple manual relative repositioning sequences between the camera inspection system viewing port and areas of interest within the turbine by a human inspector. Inspection quality and productivity is subject to the inspection and manipulation skills of the inspector and inspection team. Inspection apparatus positioning is challenging due to the complex manipulation paths between components in a gas turbine. For example, insertion of a bore scope through a combustor inspection port in order to inspect the leading edge of first row vanes or related supports requires compound manipulations Improper positioning of inspection apparatus within a turbine potentially can damage turbine internal components. Often an inspection team of multiple operators is needed to perform a manual inspection using known inspection methods and apparatus. In summary, known manual camera inspection procedures and inspection system manipulation are time consuming, repetitive in nature, and often require assistance of an inspection team of multiple personnel. The “human factor” required for known manual camera inspection procedures and inspection system manipulation introduces undesirable inspection process variances based on human skill level differences. Given human skill variances, some inspection teams are capable of completing inspections in less time, achieve better image quality and have lower inspection damage risk than other teams. Ideally skills of a high performing inspection team could be captured for use by all teams.
It is desirable to obtain inspection images of the leading edges of Row 1 blades in either gas or steam turbines, as they are often the most susceptible to operational thermal and/or mechanical damage. If images of the Row 1 blade leading edges can be obtained early and easily in the earliest possible stages of the cool down cycle—for example while the rotor is spinning at under 1000 RPM before the long turning gear mode part of the cool down cycle—blades needing repair can be prioritized for replacement, refurbishment and/or other repair days before the turbine rotor comes to a complete rest. Known bore scope inspection systems experience optical quality degradation within the fiber optic scope between the scope field of view (FOV) and the camera's objective lens and maintain constant illumination during an inspection procedure. These known bore scope physical constraints effectively limit their usefulness to obtaining images of static components; in other words when the rotor is at a complete stop. Otherwise the scope camera captures blurred images of the rotating blades.
A need exists in the art for optical camera inspection systems and methods that enable visual inspection of all Row 1 blades from a single, easily accessed inspection point while the turbine rotor is rotating at up to 1000 RPM.
An additional need exists in the art for optical camera inspection systems and methods that reduce total time necessary to perform a nondestructive internal inspection of power generation machinery, including by way of non-limiting example steam or gas turbines and generators than is attainable by known inspection apparatus and methods, so that the machinery can be brought back on line for resuming power generation more quickly during maintenance cycles.
Another need exists in the art for optical camera inspection systems and methods that are capable of positioning inspection apparatus within power generation machinery, including by way of non-limiting example steam or gas turbines and generators, consistently and repetitively within an individual machine's inspection cycle or within inspection cycles of multiple different machines, with minimized risk of damage to machine internal components, high image quality and quicker inspection cycling time than is attained by the known manual inspection apparatus and methods.
Yet another need exists in the art for optical camera inspection systems and methods that help to equalize inspection skill level and productivity among different inspection teams.